Bottom Electrode Mask Layout for MRAM ILD Delamination Control
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Solution Overview
Problem
In MRAM device fabrication, the thinning of interlayer dielectric (ILD) layers leads to delamination and etch chemical leakage issues during CMP processing, due to lack of etch selectivity and over-etch non-uniformity, which complicates the minimization of word line to MTJ distance for improved writing efficiency.
Innovation Solution
A novel bottom electrode (BE) mask layout with a substructure including metal layers and insulating layers, featuring a unique pattern with active and dummy BE elements, is used to enhance etch thickness uniformity and reduce delamination by adding dummy BE elements for additional coverage and protection of the etch stop ILD layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the ILD layer thickness is reduced to minimize the word line to MTJ distance, then the writing efficiency is improved, but the ILD layer becomes susceptible to delamination during CMP processes and etch chemical leakage increases
Solution Approach 1:
The patent applies preliminary action by forming an etch stop layer beneath the ILD layer before thinning the ILD to minimal thickness. This pre-established protective layer prevents delamination during subsequent CMP and etching processes, enabling the use of ultra-thin ILD layers without compromising structural integrity.
Solution Approach 2:
The etch stop layer serves as an intermediary between the thin ILD layer and the underlying structures. It mediates the mechanical and chemical stresses during CMP and etching processes, protecting the vulnerable thin ILD layer from delamination and chemical attack while allowing the desired thin geometry to be achieved.
2Manufacturing precision
If the ILD layer is thinned to improve device density, then the manufacturing precision is improved, but the etch selectivity between BE and ILD films is insufficient leading to over-etch non-uniformity
Solution Approach 1:
The etch stop layer acts as an intermediary that provides the necessary etch selectivity barrier. It has distinct etching characteristics that differ from both the ILD and BE layers, allowing selective removal of ILD material while protecting the BE layer, thereby achieving uniform thickness control without compromising ease of manufacture.
Solution Approach 2:
The patent changes the material parameter of the structure by introducing an etch stop layer with specific material properties that provide differential etch rates. This parameter change enables selective etching processes to achieve precise ILD thickness control while maintaining compatibility with existing manufacturing processes.
3Productivity
If the ILD layer thickness is reduced to maximize writing efficiency, then the device performance is improved, but pinholes and etch chemical leakage through the ILD layer increase
Solution Approach 1:
The etch stop layer serves as a protective intermediary that prevents etch chemicals from penetrating through pinholes in the thin ILD layer to reach and damage the underlying BE layer. It blocks the harmful chemical leakage pathway while allowing the thin ILD geometry to be maintained for high writing efficiency.
Solution Approach 2:
The etch stop layer provides beforehand cushioning by being positioned beneath the thin ILD layer to absorb and prevent the propagation of harmful effects. It cushions against etch chemical leakage through pinholes and prevents damage to critical underlying structures, enabling the use of ultra-thin ILD layers.
Data Source
AI summary
A bottom electrode (BE) layout is disclosed that has four distinct sections repeated in a plurality of device blocks and is used to pattern a BE layer in a MRAM. A device section includes BE shapes and dummy BE shapes with essentially the same shape and size and covering a substantial portion of substrate. There is a via in a plurality of dummy BE shapes where each via will be aligned over a WL pad. A second bonding pad section comprises an opaque region having a plurality of vias. The remaining two sections relate to open field regions in the MRAM. The third section has a plurality of dummy BE shapes with a first area size. The fourth section has a plurality of dummy BE shapes with a second area size greater than the first area size to provide more complete BE coverage of an underlying etch stop ILD layer.